Printing blanket, especially for offset printing

ABSTRACT

A printing blanket, especially for offset printing, comprising a strength carrier layer, an intermediate layer, and an ink transfer layer comprising a polymer base, filler materials containing hydroxyl groups, and high molecular weight, surface active substances.

United States Patent 1191 June 25, 1974 Sohnemann PRINTING BLANKET,ESPECIALLY FOR 161/401 OFFSET PRINTING [75] Inventor: Richard Sohnemann,Northeim, [56] References Cited Germany UNITED STATES PATENTS [73]Assignee: Continental Gummi-Werke 3,235,772 2/1966 Gurin 161/401Aktiengesellschaft, Hannover, 3,676,282 7/1972 Volmer l6l/401 Germany 22Filed; N0 2 1972 Primary Examiner\l Villiam J. Van Balen [21] A 1 NO 310093 Attorney, Agent, or Fzrm-Walter Becker 0 [57] ABSTRACT [30] ForelgnApplication Pnomy Data A printing blanket, especially for offsetprinting, com- NOV. 29, 1971 Germany 2159085 p g a Strength carrier y anintermediate y and an ink transfer layer comprising a polymer base, [52][1.8. CI 161/162, 161/401, 161/160, finer materials containing hydroxylgroups and-high 51 1 lm Cl i /i molecular weight, surface activesubstances. [58] Field of Search 161/160, 161, 162, 87, 7 Claims, 1Drawing Figure O O O PRINTING BLANKET, ESPECIALLY FOR OFFSET PRINTINGThe present invention relates to printing blankets, especially foroffset printing, with an essentially nonductile strength carrier layer,an if necessary volume compressible intermediate layer, and a dye or inktransmitting layer.

In the past, the quality of printing products in offset printing wasconsiderably improved by means of constructive measures with thedesigning of the strength carrier layer and the intermediate layer ofblankets. However, one of the main difficulties were encountered withregard to the coordination of the properties of the dye transmittinglayer of the blanket, the printing ink, and the ink carriers to eachother. Thus, frequently, with a change of the ink carrier to be printedupon and/or the ink, a herewith coordinated blanket must be mounted uponthe printing cylinder of the machine.

A certain amount of improvement could be obtained by forming the uppersurfaces of the blanket as smooth as possible to reduce the absorptionof water. Thusit has been suggested, for example, to make the uppersurfaces of the blanket water repellent by means of a lacquer coatingand to obtain a largely smooth upper surface. These coating measures,however, are very sensitive to mechanical influences, so that theimprovement of the printing style is obtained at the expense of a highlyreduced life expectancy.

Three parameters may be considered critical for the behavior of theblanket during printing in relation to the upper surfaces, namely:

1. The critical upper surface tension, which is proportional to thewettability by ink and water,

2. The roughness of the upper surface, and

3. The electrical charge, which in addition to the upper surfacemovements can often be made responsible for the adhesion of the paper tothe rubber blanket.

It is therefore an object of the present invention to produce an inktransmitting layer for blankets which are especially suitable for offsetprinting, and in which the dye transmitting layer in addition to havinga good resistance against mechanical influences, will also have a smoothpaper repelling upper surface, and will be able to maintain its criticalupper surface tension as well as its upper surface conductivity over along period of time.

These and other objects and advantages of the invention will appear moreclearly from the following specification in connection with theaccompanying drawing showing a section through a printing blanketaccording to the present invention.

As exemplary of the blanket according to the invention, the blanketshown in the drawing consists of an in necessary multi layer strengthcarrying layer 1 provided with an if necessary porous intermediate layer2, which is coated with a dye or ink transmitting layer 3 constructedaccording to the invention.

The blanket according to the present invention is characterizedprimarily in that the ink transmitting layer is constructed upon a baseof polymers which essentially correspond to those used in theintermediate layer or at least are excellently fusable with them. Themass or material made upon the base of this polymer and used to form theink transmitting layer has a concentration between 50 and per cent byweight, with regard to the polymer portion of the material, of bright ortransparent filler material containing hydroxyl groups. The materialalso preferably contains antistatic, high molecular, surface activesubstances in a proportion of between 1 and 15 per cent by weight,likewise with reference to the polymer content.

The selection of surface active substances is especially criticalbecause materials are involved which separate from the mixture and arecontinuously removed from the surface during cleaning of the blanket aswell as during the printing itself. Materials with too small a molecularweight permit only small doses, are very quickly bleached or washed out,and arrive, in this connection, in too large of a concentration in thedamping solution as well as in the printing ink.

On the other hand, it is known that high surface activity need notalways be combined with good conductivity. A number of materials, whichare known as surface active and anti-static, show no long durationeffects because they exhibit too high of an incompatability with thepolymer and thereby too high of a migration velocity. It has been proventhat for example polyethylene oxide, polyethylene oxide condensates,polyethylene glycol ethers and polyglycol esters, amines, aminopolyethers, quaternary ammonium salts, sulfonated organic compounds,such as for example, sulfonated paraffin and the like, are onlyeffective over a limited period of time.

However, it has been found that a number of these materials in mixtures,which, as filler material contain magnesium silicate containing hydroxylgroups and additional polyglycols with molecular weights between 5,000and 20,000, migrate at a considerably slower rate and in additionthereto can be incorporated into the mixture in larger amounts so thatthey can remain effective over a considerably greater period of time andthereby can increase the life expectancy of the blanket.

It can be taken for granted that the magnesium silicates which containhydroxyl groups and/or high molecular polyglycols improve thecompatability of the mixture for the surface active substances andincrease their conductivity.

The thickness of the layer of the ink transmitting layer constructedaccording to the invention should amount to at least 0.01 to 0.02millimeters, preferably 0.05 millimeters, in order to produce in thelayer a suf ficient deposit of slowly migrating surface active substanceand to assure a better elimination of the electrostatic charges.

Butadiene-acrylonitrile mixed polymerizates are preferred as polymers.To obtain the surface smoothness, the polymers contain an admixture ofthermoplastic synthetic materials, such as for example polyvinylchloride, chlorinated polyethylenes, polyamides or the like. To improvethe hydrophile, or affinity for water, the polymers contain fatty acidmodified, constantly swelling factices (rubber substitutes) upon acastor oil base.

The selection of the filler material shows greater influences than canbe at first expected. Bright or transparent filler materials, especiallysilicates, have shown themselves superior to carbon black. Especiallyfavorable is the insertion of a magnesium silicate containing hydroxylgroups (a vapor talc known under the trade mark Mistron).

The combined use of filler materials containing hydroxyl groups andpolyglycols with molecular weights between 5,000 and 20,000 permits ahigh dose of surface active substances and apparently also a control oftheir migration velocity, so that even with a layer thickness of only0.01 to 0.02 mm, a sufficient deposit of surface active substances maybe formed, which remains throughout the life of the blanket.

The coating measures formed according to the invention may bemanufactured in a customary manner and applied to the surface of theblanket.

The mixture formed according to the invention may be made in a customarymanner and applied. The invention will be further illustrated by thefollowing examples:

EXAMPLE 1 In an internal mixer at a temperature between 140 and 150 C, ablend is made of 100 parts by weight butadiene-acrylonitrile mixedpolymerizates (28 to 38 percent acrylonitrile) with 30 parts by weightof polyvinyl chloride in the form of a polymerizate suspension. Aftercooling to about 90 C, 50 parts by weight of a fatty acid modifiedfactice upon a Castor oil base and 25 parts by weight of a polyglycolester of fatty acids of average chain length are mixed in. After afurther cooling to about 70 to 80 C, 3 parts by weight of a polyglycolhaving a molecular weight of 5,000 to 20,000, one part by weight ofparaffin wax and seven parts by weight of sulfonated paraffin, one partby weight of stearic acid and one part by weight of a phenol ageresistor as well as five parts by weight of zinc oxide are mixed in,whereupon at the same temperature 85 parts by weight of a magnesiumsilicate containing hydroxyl groups (Mistron vapor talc) are mixed in.Finally, at a temperature between 50 to 60, 1.5 parts by weight sulfuras well as three parts by weight of accelerators or catalysts of themercaptoand thiuram classes are mixed in. The mixture obtained is workedinto a brushable paste through the addition as solvent of ethyl acetatetoluene (1:3). The resulting mixture is applied to the prepared blanketfoundation in a layer having a thickness of about 0.02 mm, and the thusobtained product is vulcanized.

EXAMPLE 2 A rubber mixture is made according to the procedure describedin detail in example 1, and consists of the following:

Parts by Weight Butadienc-acrylonitrile mixed polymerizate -ContinuedParts by Weight sulfonated castor oil 1 l thiuram sulfide classes 3Sulfur Vulcanizates of this mixture show the following physicalproperties:

Strength (DIN 53504) kp/cm Expansion (DIN 53504) 600% Shore hardness A70 upper surface resistance 10*0- cm current-flow resistance Electricalconductivity (DIN 53596) It is, of course, to be understood that thepresent invention is by no means limited to the specific showing in thedrawings or in the examples, but also comprises any modifications withinthe scope of the appended claims.

What I claim is:

1. A printing blanket, especially for offset printing, which comprises astrength carrier layer, an intermediate layer, and an ink transferlayer, said ink transfer layer comprising a polymer base, bright fillermaterial containing hydroxyl groups, and surface active substanceshaving high molecular weights.

2. A blanket according to claim 1, in which said filler material ispresent at the rate of from 50 to per cent by weight in relation to saidpolymer content.

3. A blanket according to claim 1, in which said surface activesubstances are present at the rate of from 1 to 15 per cent by weight inrelation to said polymer content.

4. A blanket according to claim 1, in which said sub stances arepolyglycols having molecular weights ranging between 5,000 and 20,000.

5. A blanket according to claim 1, in which said filler material ismagnesium silicate.

6. A blanket according to claim 1, in which said surface activesubstances are anti-static.

7.'A blanket according to claim 6, in which said substances aresulfonated paraffin, sulfonated castor oil,

and ethylene oxide condensates.

2. A blanket according to claim 1, in which said filler material ispresent at the rate of from 50 to 150 per cent by weight in relation tosaid polymer content.
 3. A blanket according to claim 1, in which saidsurface active substances are present at the rate of from 1 to 15 percent by weight in relation to said polymer content.
 4. A blanketaccording to claim 1, in which said substances are polyglycols havingmolecular weights ranging between 5,000 and 20,000.
 5. A blanketaccording to claim 1, in which said filler material is magnesiumsilicate.
 6. A blanket according to claim 1, in which said surfaceactive substances are anti-static.
 7. A blanket according to claim 6, inwhich said substances are sulfonated paraffin, sulfonated castor oil,and ethylene oxide condensates.